Yes, there is a rounding/truncation when you write metadata to files.Another instance:My GPS Latitude is 48,50,1999664307 NAfter writing metadata to files it's now: 48,50,20NNot sure my calculations are right, but it seems that's an error of 37 meters (please correct me if I am wrong...)

So, yes again, you get corrupted values, even if the precision is probably good enough for most geotagging uses of a photo library (unless my calculation is false...)

If keeping the original values is crucial for you, I could imagine keeping the original and doing your tagging and writing metadata to files to a copy in a stack or version set.